woody debris
Ref: L06i

Definition: Whole trees or branches which fall into streams and rivers from woodland lining the river bank are known as ‘woody debris’.

Woody debris in a river

Woody Debris can cause problems as well as offering benefits for wildlife, below are some points that river managers need to consider before any action is taken:

1) Are the tree roots attached to the bank? If they are leave it, if they are not remove the tree.

2) Is the tree directing the current into a vulnerable riverbank and causing excessive erosion? If not then leave it, if yes remove the tree.

3) Is the woody debris creating a total blockage for salmonid (F02) migration? If the answer is yes, remove it, if no, leave it.

Here are some of the benefits of Woody Debris in a stream or river

• It creates pools which are vital for fish in their life cycle (F02).
• It provides cover and living space for young fish and protection from predators.
• It helps contribute to stream diversity in temperature, flow and habitat
• It can help with oxygenation (G1) of water
• It provides a good habitat for mini-beasts which fish eat (see Mini-beasts B09a and Food Web B06d).